An LTE (Long Term Evolution) of which the specifications are designed in 3GPP (3rd Generation Partnership Project), which is a project aiming to standardize a cellular communication technology, supports a cellular/WLAN radio interworking technology in Release 12 and later (see Non Patent Document 1 and 2).
With such a technology, a user terminal performs, on the basis of a determination condition regarding received power or reception quality of a cellular received signal and a determination condition regarding WLAN, terminal-initiated switching control to switch traffic of the user terminal between cellular communication and WLAN communication. The determination condition is determined by a threshold value (RAN assistance parameters) designated by a cellular network (RAN: Radio Access Network).
Further, in order to enhance the cellular/WLAN radio interworking technology, a technology is proposed by which traffic belonging to an identical data bearer is transmitted and received by using both the cellular communication and the WLAN communication (hereinafter, referred to as “cellular/WLAN aggregation”) (see Non Patent Document 3).